Getting the LM3914N to work!
So first, not only did JohnS_AZ send this to me, he, along with many of the @savagecircuits IRC crew, have been helping me try to troubleshoot this deceptively simple circuit.
So here was the circuit I was trying to put together:
Oh the issues!
Simple right? Well, as long as everything works and you have the right voltages and connections! I hooked up a 9v battery to the circuit but the LED bar acted really really strangely. My original audio input was a 1/4" jack hooked up to a cigarbox guitar.
The LEDs didn't seem to light up when I played the guitar. In fact, these LEDs look kinda dim...maybe I need more than 9 volts going to the power rail. So then I added a 4.5v battery pack to the power rail that already had the 9v attached to it, asked the IRC folks if that was a totally noob thing to do, and they essentially said yes. BUT suggested that I could put the power sources in series. So I did that and ended up with a 13.5v power rail. Well, the LEDs still didn't work properly.
So then I thought well, power to the whole thing isn't working, maybe there's not enough voltage going to the input signal pin. Maybe I need to up the ante. So I made a LM386 amp and attached the guitar input to that! Still nothing.
Well maybe the LM386 amp wasn't wired properly. I'll just put a speaker to it and see if it works. It does work! But no led love yet.
Well maybe it still needs more power, lucky for me we just made a preamplifier! So I put the output of the preamp to the amp, the output of the amp to the input signal pin of the led driver. Annddddd....still no dice.
So we were thinking, well maybe it's the chip. @JohnS_AZ drew up a schematic to test the functionality of the chip as a voltage divider to make a variable 0 to 9 volt signal. He said that he also did a LM386 amp attached to it and he had to crank up the volume to get even a few of the LEDs to light up.
Alright so I made this and in doing so found out a few interesting and relevant tidbits from John about the pins on this chip that helped me figure a few things out.
Pin 9 - This is known as the MODE pin. Why? Well, if you connect pin 9 to the power rail, it goes into bar mode. But if you connect pin 9 to the ground rail, it goes into dot mode. (Dot mode is where only one led is lit at a time)
Bar:
Pin 5 - This is where your signal goes into. But you can also "zero" where the start of the voltage measurements occur. So if for instance you hook everything up, and you see that without a resistor to "temper" the input signal, 5 led bars are already lit. Using a potentiometer also connected to pin 5, you can zero that down.
Pin 7 - Formally known as Vref - this pin helps to determine LED brightness. Cool.
Anyway it works now! YAY! Thanks again to @johns_az for his unending patience as well as @ajfabio, @jrspruitt, and @tymkrs for helping me troubleshoot this as well as all of the other folks who helped.
@atdiy/@tymkrs